Share This

Microbiologists at UT Southwestern Medical Center, working with the Department of Agriculture, have identified a potential target in cattle that could be exploited to help prevent outbreaks of food-borne illnesses caused by a nasty strain of Escherichia coli.

Related Articles

In the study, available online and in an upcoming issue of the Proceedings of the National Academy of Sciences, researchers interfered with a genetic sensing mechanism that allows the E. coli strain known as enterohemorrhagic O157:H7, or EHEC, to form colonies within cattle, causing the bacteria to die off before they could reach the animals' recto-anal junction, the primary site of colonization. Most other strains of E coli gather in the colon.

"We're diminishing colonization by not letting EHEC go where it needs to go efficiently," said Dr. Vanessa Sperandio, associate professor of microbiology and biochemistry at UT Southwestern and senior author of the study. "If we can find a way to prevent these bacteria from ever colonizing in cattle, it's possible that we can have a real impact on human disease.

"This could be something as simple as including some sort of antagonist in cattle feed, which would result in less shedding of the bacteria in fecal matter with less contamination down the road in food products."

Dr. Sperandio said the finding is important because an estimated 70 percent to 80 percent of the cattle herds in the U.S. carry EHEC.

Although EHEC can be a deadly pathogen to humans, the bacterium is part of cattle's normal gastrointestinal flora. EHEC harbors a gene called sdiA, which makes the SdiA protein. The SdiA protein senses a chemical made by microbes in the animal's rumen, the first of a cow's four stomachs, which serves as a large fermentation chamber. Detecting this signal allows EHEC to pass through the rumen and colonize the recto-anal junction.

For the study, the researchers injected two types of EHEC into the rumens of eight grain-fed adult cows. One mutant version lacked SdiA and could not detect the signal in the rumen. Another strain produced an enzyme that destroyed the chemicals in the rumen sensed by SdiA.

The researchers found that colonization diminished significantly when these EHEC strains were unable to sense the rumen chemicals. The process prevented the bacteria from moving on through the stomach and colonizing.

"If there's no signal, then there's no acid resistance, a requirement for the pathogen to make it to the recto-anal junction," Dr. Sperandio said. "Everybody had thought that this type of signaling occurred naturally in the gastrointestinal tract of mammals. Our finding serves as a proof-of-principle that we might be able to target this system to prevent food contamination."

EHEC, like other E coli strains, is usually transmitted through contaminated food. Recent outbreaks in the U.S. have been found in ground beef, spinach and raw sprouts. EHEC is responsible for outbreaks throughout the world of bloody diarrhea and hemolytic uremic syndrome -- a condition that can lead to renal failure and death. Severe symptoms are most common in children, the elderly and immune-suppressed people.

Cattle are the primary source for most E coli infections in the U.S. When cattle waste reaches water sources near food crops, contamination can occur. Unsanitary slaughtering of cattle also can lead to cross-contamination of the beef itself, and shipment of infected food speeds the rate at which the public can become ill.

Dr. Sperandio said the next step is to assess what happens to cows fed a grass-based, rather than grain-based, diet.

Other UT Southwestern researchers involved in the study were Dr. Darya Terekhova, postdoctoral researcher in microbiology; and Dr. David Hughes, lead author and former graduate student in microbiology. Dr. Hughes is now at the University of Miami.

Researchers from the University of Idaho, UT Dallas, the USDA Agricultural Research Service and the University of Maryland School of Medicine also contributed to the study.

The study was funded by the National Institutes of Health, Burroughs Wellcome Fund, and the National Cattlemen's Beef Association.

Mar. 3, 2015 — Why do people shake hands? A new study suggests one of the reasons for this ancient custom may be to check out each other's odors. Even if we are not consciously aware of this, handshaking may ... full story

Mar. 3, 2015 — It appears that stress markers in unemployed people can be found, independent of smoking, alcohol consumption and overweight/obesity. Results from a study suggest that long-term unemployment may be ... full story

Mar. 3, 2015 — Doctors write millions of prescriptions a year for drugs to calm the behavior of people with Alzheimer’s disease and other types of dementia. But non-drug approaches actually work better, and carry ... full story

Mar. 3, 2015 — Briefly counseling college students on the dangers of binge drinking is effective in lowering heavy drinking levels among many students, but only temporarily. Three out of four will be right back ... full story

Mar. 3, 2015 — Body mass index in healthy adolescents has a statistically significant association with both systolic blood pressures and diastolic blood pressures, research shows, and it highlights the significance ... full story

Mar. 3, 2015 — Loneliness brought about by the death of a spouse can trigger a wider network of depression-like symptoms, a study has found, but authors suggest that doctors are often too quick to attribute these ... full story

Mar. 3, 2015 — Family Based Interpersonal Psychotherapy (FB-IPT) is more effective in treating preadolescent children with depression compared to child-centered therapy (CCT), a recent study has found. ... full story

Mar. 3, 2015 — Two of the four known groups of human AIDS viruses (HIV-1 groups O and P) have originated in western lowland gorillas, according to new research. The scientists conducted a comprehensive survey of ... full story

Featured Videos

Mom Triumphs Over Tragedy, Helps Other Families

AP (Mar. 3, 2015) — After her son, Dax, died from a rare form of leukemia, Julie Locke decided to give back to the doctors at St. Jude Children&apos;s Research Hospital who tried to save his life. She raised $1.6M to help other patients and their families. (March 3)
Video provided by AP

Woman Convicted of Poisoning Son

AP (Mar. 3, 2015) — A woman who blogged for years about her son&apos;s constant health woes was convicted Monday of poisoning him to death by force-feeding heavy concentrations of sodium through his stomach tube. (March 3)
Video provided by AP

Related Stories

Dec. 10, 2014 — Microbiologists have identified key bacteria in the gut whose resources are hijacked to spread harmful foodborne E. coli infections and other intestinal illnesses. The Centers for Diseases Control ... full story

June 16, 2014 — Diagnosticians are helping the cattle industry save millions of dollars each year by developing earlier and accurate detection of E. coli. "Developing a method to detect E. coli before it can ... full story

Apr. 15, 2014 — Between 20-30 percent of food-poisoning outbreaks linked to disease-causing strains of the bacterium Escherichia coli are caused by people eating contaminated vegetables. Research shows that the ... full story

Aug. 6, 2012 — A commercial vaccine for cattle can effectively reduce levels of E. coli O157:H7 by more than 50 percent, a new study has found. The vaccine is also effective using two doses instead of the ... full story

May 19, 2011 — After corn is processed to make ethanol, what's left of the corn looks something like slightly dampened cornmeal, though a somewhat darker yellow, and not as finely ground. Known as "wet ... full story

ScienceDaily features breaking news and videos about the latest discoveries in health, technology, the environment, and more -- from major news services and leading universities, scientific journals, and research organizations.